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Re: [TRNSYS-users] solar hort water system trnsys 16.01
Javier,
There is a discussion of some of the difficulties associated with
modeling controllers with discrete time steps in section 5.1 of the
05-Mathematical Reference manual.
Another problem that you may be having is insufficient thermal
capacitance in your system, particularly if you have a collector loop that
consists of a pump, collector, and heat exchanger. You need to make sure to
include enough piping in the loop to store at least 1 time step of fluid.
Without the piping, there is no capacitance in the loop (assuming that you
are using the Type1 solar collector or some other model that does not
include capacitance effects) and the controller will have an impossible
time converging on a decision without coming up against its oscillation
limiting parameter. The "high limit cut out" parameter may also be a
problem. If your collector temperature gets above the high limit cut out
temperature then the controller automatically shuts off the pump for that
time step. The following time step, the controller tries again and may turn
the pump on, leading again to oscillations.
Kind regards,
David
At 05:10 4/27/2006, javier mota wrote:
Dear all:
i am javier mota from 3i-ingenieria, madrid
we are looking the file "solar hot water system" in trnsys
16.01(FILe>new>solar hot water system)
we have looked the behavieour of pumps, signal control, of controller.
we have seen that some times controller must be on because T
upper-tlower>death band but in this circumstances controller signal is off.
We look too that even when the off condition is not reached beacuse
Tupper-tlower<death band lower is not correct the controller is of. For
example death band=0;
Tupper>tlower and pumps stopped.
I suspect that this may have relation with parameter 1: oscilation, but
really i don´nt know.
May anybody tell me something about this.
where can i founf more information about controller.
may i think that even of this things program works properly?
thanks in advance
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